This invention relates to improvements in pallets, particularly metal pallets.
The modern pallet, as we now know it, got its start with the invention of the forklift, which was used extensively during the World War II, when the military needed to move large amounts of materials over long distances. To do this loads were made up into unitized segments placed on pallets, which were then loaded and unloaded to and from trucks with forklifts. This was the start of modern day materials handling as we now know it.
Although pallets have been made from various types of materials from the start, wood has been the most common material used because of the low cost, availability of material, and the ease of building a variety of sizes. These advantages in the past outweighed the disadvantages, but in recent years wood pallets have become more costly as the lumber they are made from becomes less available and the proper disposal of these pallets becomes harder. Society today is more aware of the environment and is trying to find various techniques that are not only beneficial to the environment but are cost effective.
The materials handling industry is now demanding more from pallets; this industry wants economy, durability, uniformity, and increased safety. A wood pallet cannot satisfy these requirements.
Several manufacturers have introduced pallets made from plastic materials. These have found use in various applications but have a number of disadvantages in that the plastic materials can crack or chip and these pieces can fall off and jam conveyors or palletizers. Most plastic pallets are not suitable for unsupported or edge racking owing to insufficient strength and extreme deflection. Plastic pallets also become brittle in cold temperatures and subject to breakage.
Metal pallets have come into use to some degree over the past number of years but in the past the drawbacks of metal pallets have outweighed the benefits. Typical prior art metal pallets were heavy, costly, and mainly intended to be used as in-house pallets. Major problems encountered with prior art pallets include the possibility of weld breakage under heavy prolonged use with the result being that the component parts of the pallet work loose and may escape from the pallet altogether with unfortunate results. Additionally, many pallet designs pose a safety hazard owing to the fact that certain raw edges are exposed and can cause injury to personnel. Certain designs also failed to offer true four-way entry for both pallet jacks and forklifts, i.e. the pallets were not accessible from both sides and both ends.
Reference may be had to published International Application WO86/00866 which discloses a metal material handling pallet having a deck of corrugated planks and a spaced parallel base also of corrugated members both of which are welded to cross bearers. Each bearer comprises a pair of U-shaped channels welded back-to-back via their web portions. A suggested modification involves the use of closure plates which are welded across the ends of bearers, the closure plates having side flanges that are welded to the leg portions of the bearers and end caps which engage-over and are welded to the side channels of the deck and the base.
Reference may also be had to U.S. Pat. No. 2,152,086 which discloses a metal pallet having opposed parallel decks and comprising corrugated members with special profiles extending along both sides of the pallet and defining U-shaped flanges which engage and cover up the edges of the corrugated members.